1. Field of the Invention
The present invention relates to methods for micropatterning a surface of a semiconductor wafer and, more particularly, to a method and an electro-optical apparatus that performs microlithography by electronically generating a mask pattern.
2. Description of the Prior Art
Optical lithography, otherwise known as photolithography, is a process which transfers a pattern of primary electronic or optical elements to a surface of a semiconductor wafer. This process of pattern transfer, or masking, is repeated many times during the fabrication of an integrated electronic circuit or an integrated optical device. During this process, an entire surface of a wafer is coated with a photosensitive emulsion known as photoresist. The photoresist coated wafer surface is then optically exposed in a desired geometric pattern which forms the primary electronic or optical elements. This process, as it is applied to the fabrication of microelectronics and microoptics, is termed microlithography.
Conventional microlithography is generally performed with a projection scheme that utilizes a precise photographic masking plate to project, using a lamp or a laser, a pattern of microelements onto an emulsion treated semiconductor wafer surface. An alignment of the projected mask pattern with fiducial marks or other features on the wafer surface requires a process that detects an alignment error between the projected pattern and the fiducial marks, and subsequently corrects this error. This alignment process is generally performed by an electromechanical actuation system. Such an electromechanical alignment system is a complex and expensive way to achieve overlay registration. Also, a photographic masking plate is expensive and subject to defects and contamination. It is therefore desirable to perform microlithography without an electromechanical alignment system or a photographic masking plate.